This invention relates to an intermittent drive for typewriters, calculators or similar machines, and more particularly to the drive for machines having a single-element type carrier.
To obtain good quality printing in typewriters, calculators or similar machines, all printing parts must be properly synchronized throughout the printing cycle. Since some parts must move relative to other parts to which they are mechanically linked, reflected forces generated by the relative motion must be controlled or limited so as not to interfere with the synchronization.
One known drive employs a continuously rotating drive part which intermittently engages a driven part by means of a wrap spring clutch. The drive is provided with a friction brake such as that disclosed in German publication DT-AS 1,802,486, to Rolf Moritz, in order to control inertial forces developed by the driven part.
A major drawback of this drive is its inability to control forces which are reflected back through the driven part while the clutch is engaged. Since the wrap spring clutch is a one-way clutch, when it is engaged forces which are reflected back from the driven part to the drive part are not transmitted to or braked by the drive part, and the driven part momentarily leads the drive part, resulting in a lack of synchronization. The driven part is particularly susceptible to reflected forces when the driven part is required to transmit multiple forces, such as when the driven part simultaneously triggers two synchronized cams which present identical profiles, which are disposed at 180.degree. with respect to each other, and which transmit motion in the same direction.
Other drawbacks of the drive described in the Moritz publication are its large size, multiplicity of parts and high cost.